1. Field of the Invention
This invention relates, in general, to depth determining and control devices, and in particular to devices for determining increase of cable length needed to reach a given vertical depth with a lure, because of cable slope due to water currents, boat speed, and other factors.
2. Description of the Prior Art
Electronic depth finders have long been used to determine vertical depth from the transducer of the depth finder, which is usually mounted in the bottom of a boat, to schools of fish; to river, lake, or ocean bottom; or to other objects located below water level. Because of water currents; the speed of the boat, as is the case in trolling; and the amount of line or cable drag, one does not know whether the lure is at proper depth determined by the depth finder because of the slope of the line or cable from vertical.
It is therefore highly desirable to be able to determine with accuracy the increase in cable length needed to accommodate for the cable slope for fishing at the desired depth.
Outriggers, and more particularly outriggers having a base; a two-section boom including a fixed section attached to the base and a rotatable section, rotatably mounted about the longitudinal axis of the boom; a reel; cable; and cable pulley are well known in the art. Also known in the art is the invention of E. J. Swan, U.S. Pat. No. 3,786,586, which includes a plate which is held in the horizontal position and which has a plurality of sloped lines which one compares with the slope of the cable while trolling to determine a first reference. One then checks a chart, displayed on the plate, to compare the first reference with the depth desired for determining length of line needed to reach a given vertical depth. The problem encountered with the Swan device is the gross inaccuracy due to several factors. First, the plate must be held in the horizontally level position, which is difficult because of a lack of a leveling device. Horizontal leveling must therefore be by sight which is particularly difficult while ocean fishing due to the pitch and roll of the boat and the presence of waves. Secondly, the plate must be held in a vertical position which is difficult for the same reasons. Thirdly, the slope of the cable must be compared to the lines on the plate by sighting through the plate. For accuracy, the sighting should be with the eye of the observer; the indicia line on the plate; and the liner cable for the outrigger all being on the same level--a virtual impossibility because the gunwale of the boat is most often too high relative to the cable to allow such sighting and the inconvenience of lowering the eye to the level of the cable is also obvious. Fourthly, the plate must be held in alignment with the boat for an accurate reading. This combination of factors, all of which must be performed simultaneously, renders the device of Swan impractical. A further disadvantage is the requirement of consulting a chart to determine further amount of line or cable to be payed out.